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Math Help - Don't know how to factor?

  1. #1
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    Don't know how to factor?

    Hello,

    I have the following equation:

    v1/v2 = R2/R1+R2

    How do we solve for R2?

    I don't know how to isolate R2 on one side of the equation. All help is appreciated?

    thanks
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  2. #2
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    Re: Don't know how to factor?

    [QUOTE=simplyComplex;773431]I have the following equation:
    v1/v2 = R2/R1+R2
    How do we solve for R2?/QUOTE]

    Is it \frac{v_1}{v_2}=\frac{R_2}{R_1+R_2}~?

    Because you actually posted \frac{v_1}{v_2}=\frac{R_2}{R_1}+R_2

    Which is it?
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  3. #3
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    Re: Don't know how to factor?

    If it is \frac{v_1}{v_2}= \frac{R_2}{R_1+ R_2}, start by multiplying both sides by v_2(R_1+ R_2) to get v_1(R_1+ R_2)= v_1R_1+ v_1R_2= v_2R_2.

    If it is \frac{v_1}{v_2}= \frac{R_2}{R_1}+ R_2, start by writing R_2 as \frac{R_1R_2}{R_2} so you have \frac{v_1}{v_2}= \frac{R_2}{R_1}+ \frac{R_1R_2}{R_1}= \frac{R_2+ R_1R_2}{R_1} and now multiply by R_1v_2.
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  4. #4
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    Re: Don't know how to factor?

    Ooops I'm sorry.... Its:

    v1/v2 = R2/(R1 + R2)

    start by multiplying both sides by v2(R1 + R2) to get....
    stop, you are going too fast for me!!!! If I start off with this:

    v1/v2 = R2/(R1 + R2)

    so when you say cross multiply... do you mean like this:
    (R1 + R2) (v1/v2) = (R2/(R1+R2)) (v2)
    v1(R1 + R2) = R2v2
    v1R1 + v1R2 = R2v2


    So now, R2 is on both sides, what I really need is to isolate R2 on one side!!!!
    So what is the next step?

    thanks
    Last edited by simplyComplex; March 4th 2013 at 11:11 AM.
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  5. #5
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    Re: Don't know how to factor?

    Okay I think I got it:

    v1/v2 = R2/(R1 + R2)
    (R1 + R2) (v1/v2) = (R2/(R1+R2)) (v2)
    v1(R1 + R2) = R2v2
    v1R1 + v1R2 = R2v2
    v1R1 = R2v2 - v1R2
    v1R1 = R2(v2 - v1)

    v1R1/(v2-v1) = R2(v2 - v1)/ (v2 - v1)

    R2 = v1R1/(v2-v1)

    Thanks!
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